Battery changes could take up to five days for each 787

Boeing now estimates that its proposed 787 battery modifications will consume four to five days for each aircraft, if US regulators approve the installation changes.

The task of installing the new assemblies could begin within weeks or even days now that Boeing has started flight tests to validate the results of ground and laboratory testing of the new battery changes.

If the US Federal Aviation Administration (FAA) accepts the design changes, Boeing has to install the new assemblies for both the main and auxiliary power unit batteries on about 50 787s already delivered to airlines. The changes will then be retrofitted in the 787s on Boeing's assembly lines in Everett, Washington, and North Charleston, South Carolina.

"Our baseline plan is to deliver the battery assemblies in roughly the same order as initial deliveries," Boeing says.

That means 787 launch customer All Nippon Airways and Japan Airlines will likely be the first carriers to resume flying the widebody in operational service. Both airlines, coincidentally, were struck by the two battery incidents that caused the fleet-wide grounding of the 787 since 16 January.

Boeing noted that exact timing of the retrofit work could vary.

Boeing completed a functional check flight on a LOT-ordered 787 on 25 March. A certification flight test is expected to follow by the end of the week.